1. Field of the Invention
The present invention relates generally to curable epoxy compositions and, in particular, to a water-based epoxy grout, which is commonly known as a tile grout.
2. Description of Related Art
In the installation of ceramic tiles and other tiles, the tiles are assembled in an edge-to-edge pattern with spaces between the tiles and it is necessary to fill the areas or joints between adjacent tiles with a bonding material. The material used to fill the joints is referred to as a pointing compound or more commonly as a tile grout. There are a variety of tile grout compounds including acrylic grout, epoxy grout and Portland and regular cement based grout. The following description will be directed to ceramic tiles for convenience.
Tile grouts, regardless of the type, are expected to provide certain properties. These properties include workability, stain resistance, forming a full grout in the spaces, uniform look and color and easy cleanup with a minimum amount of water. Workability is required to facilitate the spreading of the grout completely into the joint between adjacent tile edges without creating any voids or vacant areas. Workability is a very important tile grout property since it directly affects the ease of grouting the tile and grouts having a high workability are more cost effective since less labor is required to perform a tile grout job. The traditional grout is a cement containing grout which has high workability compared to conventional epoxy grouts.
The property of grout stain resistance is also important because ceramic tile is used both functionally and decoratively. Thus, permanent stains on either the ceramic tile or grout will detract from the decorative appearance of the installation. The face of the ceramic tile is essentially impervious and is therefore free from permanent stain. The grout should likewise be resistant to staining and also capable of withstanding scouring.
Easy cleanup is another important property of grout due to the nature of how tile grout is installed by the tile setter or contractor. Tile grout is installed after ceramic tiles are firmly set and is floated into the joints between the ceramic tile edges. Some of the excess grout will adhere to the tile's face or form a surface film and this grout must be removed from the tile's face without disturbing the grout joints. Cleanup is the source of the biggest complaint of tile setters.
While epoxy grout has a much higher resistance to staining than cement based grouts, it has been found in the field that installers will preferably employ a Portland cement based grout because it is much more workable and easier to clean up than an epoxy grout. Unfortunately, the Portland cement based grout is more susceptible to staining and generally stain badly, crack easily, and develop poor strength under dry conditions. Furthermore, these materials have poor acid and chemical resistance.
The highly preferred tile grout is now essentially a non-hydraulic grout and comprises a film-forming, water-dispersible, cross-linkable polymer and a curing agent. The preferred cross-linkable polymer is an epoxy and the epoxy grout mortars are essentially free of the undesirable properties which are characteristic of the aforementioned cement base grout compositions. In general, they have minimal shrinkage and become highly water and stain resistance after a period of time.
Unfortunately, as discussed above, epoxy grouts do not have the workability and ease of cleanup of cement based grouts and, while used in the industry, are lacking in wide acceptance by the installers of ceramic tiles. When cement based grouts are used, the grouts tend to crack and stain over time causing the owner to have to re-grout the tiles. This is expensive and time consuming.
Typically, the water-based epoxy grout system is a three-part system comprising an epoxy resin and a curing agent which is usually a polyamine or polyamido-amine and a filler powder such as sand and hydraulic cement. The amine groups react with the epoxide groups of the epoxy resin crosslinking the resin and forming a hardened grout. Hydraulic cement reacts with the water.
Amines, however, are relatively corrosive and the curing rate is hard to control and amine adducts, which are well-known in the art, have been developed as preferred epoxy resin curing agents. One amine adduct is “ANCAMINE 1769” (Trademark), an adduct of triethylenetetraamine with propylene oxide. This adduct is made by Air Products and Chemicals, Inc., Allentown, Pa.
More preferred amine adducts have been developed to conform to environmental regulations and one type may be defined as a polyamine-epoxy adduct. Basically, a polyamine-epoxy adduct is formed by reacting a polyamine with a polyepoxide resin using a molar excess of polyamine to form a polyamine terminated epoxy adduct. Free polyamine is typically removed and the adduct endcapped with an alkyl monoepoxide to eliminate the presence of primary amines. A portion of the remaining amine hydrogen atoms are then reacted with a salt forming component and a volatile organic or inorganic acid to enhance water solubility. The polyamine-epoxy adduct is emulsified in water and combined with an epoxy resin and the resultant mixture cured. Such an adduct is described in U.S. Pat. No. 4,246,184, which patent is hereby incorporated by reference.
Other polyamine-epoxy adduct products are disclosed in U.S. Pat. Nos. 5,246,984; 5,350,784; 5,475,039; 5,489,630; 5,508,324; 5,527,839; 5,536,775; 5,508,324; and 5,599,855; all of which are incorporated herein by reference.
U.S. Pat. No. 5,508,324, for example, discloses a number of patent references relating to water dispersible polyamine epoxy adducts which can be used as a curative for epoxy resin systems. In general, the water compatible polyamine adducts are formed by the reaction of a polyamine with a mixture of monoepoxide and polyepoxide. As discussed therein in U.S. Pat. No. 4,608,405, curing agents are described as based upon an epoxidized polyol containing aromatic and polyalkylene ether moieties in which all the epoxidized groups are reacted with a polyamine wherein each primary amine is further reacted with a monoepoxide or a monocarboxylic acid.
While this class of amine adduct is useful as epoxy curing agents, they are not used, as far as Applicant is aware, in water-based epoxy tile grouts. It is hypothesized that commercially acceptable grout systems have not been prepared using this class of adduct because of the difficulty in formulating a grout having overall good grout properties.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a water-based epoxy tile grout composition containing a polyamine epoxy adduct and a non-hydraulic filler powder which grout is stain and chemical resistant, forms a full joint in the spaces and is highly workable and easy to clean up.
It is another object of the present invention to provide methods for using the tile grout in the installation of ceramic tiles and other tiles.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.